Installing using conda

[frlacf]

Hi,

I'm new here, I think you guys made an amazing job with your FEM framework. I'm trying to install ngsolve on miniconda here is what I do:

conda create --name ngsolve --channel ngsolve

conda activate ngsolve

conda install ngsolve

Everything seems to be fine so far, ngsolve is installed, but then when I run

from ngsolve import *

I get:

importing NGSolve-6.2.2006-48-gdd7aae9c5

Caught exception:
arg(): could not convert default argument into a Python object (type not registered yet?). Compile in debug mode for more information.
Traceback (most recent call last):
File "", line 1, in
File "/home/francisl/miniconda3/envs/ngsolve/lib/python3.7/site-packages/ngsolve/init.py", line 13, in
from .ngslib import version, ngstd, bla, la, fem, comp, solve
ImportError: cannot import name 'fem' from 'ngsolve' (/home/francisl/miniconda3/envs/ngsolve/lib/python3.7/site-packages/ngsolve/ngslib.so)

Also, I have a question concerning the code. Is it possible to export/import solution in any format ? We use an FEM code for very niche applications but would like to use NGsolve's adaptive mesh refinement capabilities, so if there was a way to import results from a generic format (cgns, paraview, Ensight, Tecplot) and then use that in NGsolve to adapt the mesh, that would be cool. Anyway, great work guys.

Francis

[Matthias Hochsteger]

Hi Francis,

I think your issue is similar to the one mentioned here:
https://ngsolve.org/forum/ngspy-forum/972-conda-installers-available?start=18
The problem there is that conda installs an incompatible netgen package from conda-forge.
For now I recommend using the ngsolve-nightly package. I will hereby close this issue, reopen if you still have troubles.

NGSolve currently can export .vtk-Files ( https://ngsolve.org/showcases/ngsolve/2-vtk-output ) and import .cgns:

def LoadCGNS( fname ):                                                                                                                                                                                   
    from ngsolve import Mesh, H1, L2, GridFunction
    from ngsolve.fem import NODE_TYPE
    from netgen.meshing import ReadCGNSFile

    ngmesh, *rest = ReadCGNSFile(fname)

    mesh = Mesh(ngmesh)
    functions = []

    for name, values, node_type in zip(*rest):
        if node_type == NODE_TYPE.VERTEX:
            fes = H1(mesh, order=1)
        elif node_type == NODE_TYPE.CELL:
            fes = L2(mesh, order=0)
        else:
            print("Unknown node type for function", name, node_type)
            continue
        u = GridFunction(fes, name)

        assert len(u.vec) == len(values)

        u.vec.FV().NumPy()[:] = values.NumPy()
    
        functions.append(u)
    return mesh,functions

mesh, solutions = LoadCGNS( "the_cgns_file.cgns" )

import ngsolve
for s in solutions:
    ngsolve.Draw(s)

Best,
Matthias